Gwern has a great article [0] about commoditizing your complements as a strategy to both boost demand for your product and keep competitors at bay. (this was originally an idea put forth by Joel Spolsky).
He points out that Sun, a hardware company, was smart to work on open source window managers to make it easier to use their hardware.
In turn, they were dumb to create an open source language (Java) that could run on any hardware. This was a strange move as it dramatically reduced the need for Sun's specific machines.
Highly recommend the article as it has lots of other examples of this.